2619-Array-Prototype-Last.js

/*
https://leetcode.com/problems/array-prototype-last/

Easy

Write code that enhances all arrays 
such that you can call the array.last() method 
on any array and it will return the last element. 
If there are no elements in the array, it should return -1.

You may assume the array is the output of JSON.parse.

Runtime 57 ms Beats 57.22%
Memory 41.8 MB Beats 68.11%
*/



Array.prototype.last = function() {
    if(!(this instanceof Array)) return -1;
    if(this.length == 0) return -1;
    return this[this.length - 1];
};

/**
 * const arr = [1, 2, 3];
 * arr.last(); // 3
 */